Drop in coal power plant emissions associated with asthma improvements

In a natural experiment, researchers examined how reductions in pollution from coal-fired power plants affected local cases of asthma. Drazen_ / iStock / Getty Images Plus

Coal-fired power plants provide about a quarter of the world’s energy supply. They also release air pollutants, including sulfur dioxide, nitrogen oxides, and a type of fine particle called PM2.5.

Among people with asthma, higher exposures to these pollutants are associated with increased symptoms and more emergency room visits, hospitalizations, and deaths from the disease. Because of these and other potentially harmful health effects, regulations have aimed to reduce emissions from coal-fired power plants in the U.S.

To examine whether the resulting emission reductions correspond with improvements in asthma, researchers led by Dr. Joan Casey of Columbia University took advantage of a natural experiment that occurred in Louisville, Kentucky. Starting in 2012, a project called AIR Louisville had recruited people with asthma to use digital sensors attached to their asthma inhalers. These provided real-time information on asthma medication use. Use of asthma medication can serve as a proxy measurement of daily asthma symptoms.

From 2013 to 2016, four coal-fired power plants in the Louisville region either converted to using natural gas or installed scrubbers to reduce sulfur dioxide emissions. The researchers measured reductions in exposure to coal-fired power plant emissions over the study period and mapped them to changes in asthma symptoms among 207 people tracked by AIR Louisville. The team also looked at changes in emergency department use and hospitalizations due to asthma within the county.

The study was funded in part by NIH’s National Institute of Environmental Health Sciences (NIEHS). Results were published on April 13, 2020, in Nature Energy.

Pollution measurements confirmed that sulfur dioxide emissions dropped at all four power plants after they converted or installed scrubbers. After accounting for factors that can affect pollution levels, such as the season and weather, the researchers found that average levels of exposure to coal-fired power plant emissions in the areas fell after three of the four plant changes. By 2015, there had been a 55% decrease from the start of the study in measured emission exposure.

The three periods in which pollution dropped had fewer asthma hospitalizations and emergency room visits. The researchers estimated that almost 400 such events were avoided yearly in the county under the new pollution levels.

AIR Louisville participants also experienced an immediate drop in the use of their rescue inhalers after the final scrubber installation in 2016, by 17% compared to the month prior. Use continued to decline by 2% per month afterwards, through mid-2017.

“This study was unique in its ability to leverage an abrupt change in environmental exposure to more directly attribute changes in asthma exacerbation to changes in coal-fired power plant emissions,” Casey explains.

The study didn’t examine other air pollutants that might affect people with asthma. Sulfur dioxide represents the broader mixture of pollutants emitted by power plants. The study thus doesn’t prove which ones affected asthma outcomes. However, the results suggest that further shifts from coal-fired electricity generation could continue to reduce the burden of asthma nationwide.

—by Sharon Reynolds